Simulataneous application of charge coupled device array-detected Raman spectroscopy and differential scanning calorimetry to in situ investigation of phase transitions in condensed matter

Abstract

The combination of differential scanning calorimetry (DSC) with charge coupled device (CCD) array-detected Raman spectroscopy for the in situ investigation of phase transition is illustrated using ammonium nitrate as an example. This method aids unambiguous characterization of different phases by providing a simultaneous probe of thermodynamic and vibrational data. The availability of real-time vibrational data, including both the internal and external mode regions, is unique to array-detected Raman spectroscopy. The intensity changes of the symmetric stretching mode ν₁ of the nitrate ions and the lattice vibrations, that accompany the phase transition IV → II of ammonium nitrate, are rationalized in terms of the known crystal structure data.